Process of electrolyzing aqueous stannic-chlorid solutions.



tion. I In detinning tin-plate scrap by the action.

I with insoluble anodes.

UNITED srnt ns PATENT, 4 OFFICE.

FRANZ VON KUGELGEN, OF HOLCOMBS ROCK, VIRGINIA, AND GEORGE 0. SEWARD, OF NEW YORK, N. Y.

Specification of Letters Patent.

Patented March 24, 1908.

Application filed June 10, 1907. Serial No. 378,296.

To all whom it may concern:

Be it known that we, FRANZ VON Kii- G-ELGEN, asubject of the Emperor of Germany, residing at Holcombs Rock, Vir inia, and GEORGE O. SEWARD, a citizen oi the United States, residing at New York city, New York, have invented certain new and useful Improvements in Processes of Electrolyzin Aqueous Stannic 4 Chlorid Solu tions, of whlch the following is a specificaof anhydrous chlorin, the tin is recovered as liquid stannic chlorid. This product may be.

efi'ectively decomposed into tin and chlorin bfy dissolving it in water and electrolyzing t e aqueous solution in a diaphragm cell, Such electrolysis proceeds smoothly at first, but after a time the anolyte becomes basic and the catholyte acid, decreasing the current efiiciency, whilea gelatinous precipitate may de osit in the anode compartment. This resu t is due to the fact that stannic chlorid is partially hydrolyzed' by water, with the production of stannic hydroxid and hydrochloric acid, which are therefore The difference in t e ionic velocities causes the concentration of the base and acid in the cell compartments to gradually change during electrolysis, until the amount of stannic hydroxid in the anode compartment is in excess of that which will remain in solution in the hydrated stannic chlorid.

According to the present process, an aqueous solution of stannic chlorid is electrolyzed by placing it in the cathode compartment of a diaphragm cell, While an aqueous solution containing primarily hydrochloric acid is used in the anode compartment. The catholyte preferably consists of a stannic chlorid solution having a specific gravity of about 1.2; the anolyte of a twenty per cent. hydrochloric acid solution, which may contain a small amount oi stannic chlorid. The cell may have Walls of slate, a diaphra m of porous earthenware, anodes'of graphite and cathodes of sheet tin. The preferred current density at the cathode is 4.2 am eres per square decimeter. As the electro sis procoeds, the relatively high ionic ve ocity of the h drogen cation causes a gradual transfer 0i hydrochloric acid from the anode to the cathode compartment, until finally the currenpeiliciency begins to notably drop.

resent in the electrolyte.

At this stage the catholyte ma contain about eighteen per cent. of hydroc oric acid and a little stannic chlorid. Both solutions are thereupon removed from the cell and the old catholyte is transferred to the anode-compartment, its hydrochloric acid content be mg brou ht u to twenty per cent. by the addition 0 acid Stannic chlorid is added to the old anolyte until its specific gravity rises to 1.2 and it is then-placed in the cathode compartment. The initial cell-conditions are-thereby restored and the. electrolysis is hydrochloric acid anode solution and a tin chlorid cathode solution, until a considerable percentage of the hydrochloric acid has passed into said cathode solution, then addmg tin chlorid to said anode solution and passing an electric current through the two solutions in the opposite direction.

tin chlorid solutions, whichconsists in passing an electric current successively through an anode solution containing about twenty per cent. of hydrochloric acid and a cathode solution of tin chlorid, until a considerable percentage of the hydrochloric acid has passed into said cathode solution, then addmg tin chlorid to said anode solution and passing an electric current through the two solutions in the o posite direction.

In testimony w iereof, we affix our signa tures in presence of witnesses.

FRANZ VON KUGELGEN. GEORGE O. SEWARD. Witnesses as to the signature of Franz von Kiigelgen:

HARRY RILEY LEE, J. H. WEBB. Witnesses as to the signature of George 0. Seward? JUs'rIN C. WALKER, (.lEo. F. SEWARI)- 2. The process of electrolyzing aqueous 

